Method of manufacturing turbine diaphragms



Jan. 10, 1939. A. R. ALLARD METHOD OF MANUFACTURING TURBINE DIAPHPAGMS Filed Dec. 22, 1957 2 Sheets-Sheet 1 P a a WITNESSES! mwzzvrozz I HRTHe/R R. H14 9 RD.

ATTURNEYS.

Jan. 10, 1939. A. R. ALLARD METHOD OF MANUFACTURING TURBINE DIAPHPAGMS Filed Dec. 22, 1937 2 Sheets-Sheet 2 WITNESSES:

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W"? M W Patented Jan. 10, 1939 METHOD OF MANUFACTURING TURBINE DIAPHRAGMS Arthur R. Allard, Drexel Hill, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application December 22, 1937, Serial No. 181,089

3 Claims.

This application is a continuation in part of my co-pending application Serial No. 93,514, filed July 30, 1936, entitled Method of manufacturing turbine diaphragms.

My invention, herein disclosed, relates to elastic fluid turbines, and more particularly to the provision of a ring element secured to the free ends of a row of blades.

An object of my invention is to provide a method of casting a ring element to the free ends of a row of turbine blades.

A further object of my invention is to provide a method of incorporating the free ends of turbine blade elements within an arcuate cast structure.

Another object of my invention is to provide a method of incorporating the free ends of turbine blade elements in a cast ring element, wherein opportunity for shrinkage of the cast ring element is provided for, to avoid injurious deflection of the blade elements or cracking of the ring.

These and other objects are effected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawings forming a part of this application, in which:

Fig. l is a partial side elevation of a completed diaphragm member;

Fig. 2 shows the disk and blade structure prepared for molding;

Fig. 3 is a similar view including the mold;

Fig. 3a is a view similar to Fig. 3 but showing the side plates removed;

Fig. 4 is an elevational view of a disk member having a portion of the blade row attached thereto with the end of the cast ring cast to the disk member to prevent warping of the blade row due to shrinkage of the cast ring; and,

Fig. 5 is a view similar to Fig. 4, but showing an alternative arrangement for preventing warping of the blade row or cracking of the ring element.

While my invention contemplates broadly the incorporation in an arcuate cast structure, of the free ends of any type of blades, 1. e. inwardlyextending stationary blades, inwardly-extending stationary nozzle vanes, outwardly-extending moving blades, or outwardly-extending nozzle vanes; in the interest of conciseness, I will describe herein the application of my invention to the latter type only; and it is to be understood that the term blades is used in the general sense of members defining steam passages.

Referring now to the drawings in detail, there is shown a disk member ID, of semi-circular form,

having a recess II to provide for the spindle opening in the complete diaphragm consisting V of a pair of complementary disk members 10, I0.

After cutting a disk member ID from suitable stock, transverse grooves I3 (Fig. 4) are then formed in the periphery 12 in any suitable manner, as by milling, for the reception of inner ends of blade or vane elements It. The blades I 4 are welded, as at IS, in the grooves l3 and surplus weld metal is removed in any suitable manner, as by cutting or grinding, to provide a smooth, finished top surface of the disk member.

An outer ring it is then cast to the outer ends of the blades. 'When the blade row does not extend fully to the line of division. between the two halves of the diaphragm, the outer ring is preferably extended to and cast directly onto the periphery of the disk member ID beyond the end of the blade row, as shown at Ila in Fig. 4. Suitable means, such as tap bolts l8 screwed into the disk member ID, may be provided to secure a firm connection between the disk member and the outer ring it. The outer end portions of the blades that are cast into the outer ring are preferably formed with openings l9 to provide more secure connection therebetween.

Referring now to the casting operation, the por tion of the space between adjacent blades that is to constitute the motive fluid passage is filled with any suitable core material. Side plates 2|, shown in Figs. 2 and 3, are clamped on opposite sides of the disk member. The side plates may be positioned in any suitable manner, as by providing the same with recesses ll registering with the recess l I in the disk member In and positioning an arbor 22 in the registering recesses. The side plates are also formed with recesses 23, so as to provide core material on opposite sides of the blade row. The core material is tamped so as to extend to the cylindrical surface defined by peripheries of the side plates, the outer end portions of the blades, containing the openings 19, projecting beyond the core material for incorporation in the cast outer ring. Preferably the recesses are undercut so that they, with the periphery of the disk member and said cylindrical surface, define an arcuate space of dovetail cross-section so as to hold the core material in place.

The assembly, as shown in Fig. 2, is then placed in a mold for casting of the outer ring it. As shown in Fig. 3, the mold comprises a cope}! and a drag 25. The cope and the drag have concave cylindrical surfaces fitting the cylindrical surface of the side plates and of the core material and they cooperate with the latter cylindrical surface to provide an arcuate space 26 for the outer ring l6,-into which recess the outer ends of the blades project. The drag 25 is formed with a passage 21 extending along the recess 20 and communicating therewith at spaced intervals through passages 28. The cope 24 is also formed with a passage 29 for pouring the molten metal into the passage 21. After the casting operation, the diaphragm structure is removed from the mold, the metal filling the passages 21, 28, and 2. is broken oil from the outer ring l8, and the core material is removed. The disk member I 0 and the outer ring ii are. then finish machined to form one-half of a complete turbine diaphragm.

While, in Figs. 2 and 3, I show the side plates 2i held in position with respect to the mating mold parts 24 and 25, it is to be understood that the plates 2| may be removed after the core material is tamped in as shown in Fig. 2, the dovetail arcuate space being so formed as to present an outer cylindrical surface against which the inner cylindrical surfaces of the mating mold parts bear, as shown in Fig. 3. For example, I show the recesses 23 having counter recesses 23 so that the core 23 will have flange portions 23 serving this purpose, as may be seen from Fig. 3a.

In constructions where the blade row extends fully to the line of division between the two halves of the diaphragm, the outer ring Ilia is spaced from the periphery of the disk member ill at all points and is divided into spaced sections by spaces 3|, Fig. 5. Those spaces are provided by correspondingly spaced partitions in the arouate passage 26 in the mold.

The spaces 3| permit shrinkage of the cast ring sections without undue warping or twisting of the blades or without shrinkage cracking of the outer ring. Later, metallic filler blocks 32 .are welded in the spaces 3|, completely filling the same, and the disk member in and outer ring l6a are then finish machined to form onehalf of a complete turbine diaphragm.

From the foregoing, it will be apparent that I have devised a process of casting a ring element to the free ends of blades of a blade row which comprises providing a mold including essentially first and "second parts, which complementally form an arcuate space into which the free blade ends extend, the space so formed then being filled with molten metal to produce a cast ring element incorporating the free blade ends. The first mold part, in FlgsJ2 and 3, is comprised by portions 23 of sand or material filling the passage-forming spaces between the blades and by portions 23 extending laterally of the blade row, all of said portions having cylindrical surfaces coaxial with the axis of the blade row, and the second partbeing comprised by the portions 24 and 25 providing'a channel whose sides have cylindrical surfaces mating with the'cylindrical surfaces of the lateral portions 23 of the first part so that the cylindrical surface of the first part included between said sides of the channel and the channel complementally form the arcuate space. In other words, I provide a mold for casting a ring to the free blade ends wherein the joint between the mold parts falls on a cylindrical surface coaxial with the axis of the blade row.

WhileI have shown my invention in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:

1. The process of casting a ring member to the free ends of an arcuate row of blades attached at their other ends to the peripheral portion of a supporting member, said supporting member having fiat side surfaces and a cylindrical periphery from which the blades spring, comprising placing side plates in contact with said side surfaces so as to overlap the blades except for the tip portions thereof, said side plates having peripheral portions provided with aligned cylindrical surfaces and with arcuately recessed inner corners which cooperate with the periphery of the supporting member to form an arcuate channel across which the blades radially extend; filling said arcuate channel. including the steam-passage-forming spaces between the blades, with core material to form afirst mold member having a cylindrical surface aligned with said side plate peripheral surfaces to provide a continuous cylindrical surfacepproviding a second mold member having a channel and side walls whose edges fit lateral portions of said continuous cylindrical surface to form an arcuate space into which said blade tip portions protrude; and filling, said arcuate space with molten metal to provide a cast ring member incorporating said protruding blade tip portions.

2. The process of casting a ring member to the free ends of an arcuate row of blades attached at their other ends to the peripheral portion of a supporting member, said supporting member having fiat side surfaces and 9. cylindrical periphery from which the blades spring, comprising placing side plates in contact with said side surfaces so as'to overlap the blades except for the tip portions thereof, said side plates having peripheral portions provided with aligned cylindrical surfaces and with arcuately undercut recessed inner corners which cooperate with the periphery of the supporting member to form an arcuate channel of dovetail cross-section across which the blades radially extend; filling said arcuate channel, including the steam-passage-forming spaces between the blades, with core material to form a first mold member having a cylindrical surface aligned with said side plate peripheral surfaces to provide a continuous cylindrical surface; providing a second mold member having a channel and side walls whose edges fit lateral portions of said continuous cylindrical surfaces to form an arcuate space into which said blade tip portions protrude; and filling said arcuate space with molten metal to provide a cast ring member incorporating said protruding blade tip portions.

3. The process of casting a ring member to the free ends of an arcuate row' of blades attached at their other ends to the peripheral portion of a supporting member, said supporting member having fiat side surfaces and a cylinperiphery of the supporting member to form an arcuate channel across which the blades radially extend; said channel having its side walls spaced from the blades at either side thereof; filling said arcuate channel, including the steam-passage-forming spaces between the blades, with core material to form a first mold member hav ing a cylindrical surface with lateral portions at either side of the row of blades; providing a second mold member having a channel and side walls whose edges fit the lateral portions of the cylindrical surface of the first mold member to form an arcuate passage into which said blade tip portions protrude; and filling said arcuate passage with molten metal to provide a cast ring member incorporating said protruding blade tip portions.

ARTHUR R. ALLARD. 

